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1.
The effect of solution temperature and cooling rate on microstructure and mechanical properties of laser solid forming (LSF) Ti-6Al-4V alloy is investigated.The samples are solutions treated at 900,950,and 1000°C,followed by water quenching,air cooling,and furnace cooling,respectively.It is found that the cooling rate of solution treatment has a more important effect on the microstructure in comparison with the solution temperature.The martensite α'formed during water quenching results in the higher hardnes...  相似文献   

2.
郑晓航  隋解和  张欣  杨哲一  蔡伟 《中国物理 B》2014,23(1):18101-018101
The microstructure, martensite transformation behavior, thermal stability and shape memory behavior of Ti–20Zr– 10Ta high temperature shape memory alloy were investigated. The Ti–20Zr–10Ta alloy exhibited a reversible transformation with the high martensite transformation temperature of 500oC and good thermal stability. The alloy displayed the elongation of 15% and a maximum recovery stain of 5.5% with 8% pre-strain.  相似文献   

3.
Microstructure effect on chemical etching behavior of the annealed Ti-6Al-4V and Ti-3Al-2.5V titanium (Ti) alloys was compared with that of unalloyed commercially pure titanium. The microstructural evolution of structure phases after annealing the titanium and its alloys at temperature near and above β transus and followed by furnace cooling to room temperature was studied using optical microscope, scanning electron microscope and X-ray diffraction techniques. The microstructure study illustrates that the heat treatment enhanced partitioning effect allows extensive formation of hemispherical and near spherical pits roughened surface to be readily acquired by chemically etching the annealed α + β titanium alloys. The kinetics of the chemical etching reaction process show a linear dependence on time. The annealed α + β titanium alloys that exhibit relatively lower weight loss and thickness reduction rate illustrate less chemical activity than the annealed unalloyed titanium.  相似文献   

4.
The microstructure characteristics of laser forming repaired (LFR) Ti60 (Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-0.3Nb) as-deposited and annealed samples are analyzed. The microstructure of as-deposited repaired zone (RZ) consists of epitaxial columnar prior β grains, in which fine woven α laths and β-phase between α laths exist. The heat-affected zone (HAZ) experiences a continuous microstructural transition from duplex microstructure of the base metal zone (BMZ) to the microstructure of RZ. The presence of silicide precipitates is observed in both RZ and BMZ in an annealed sample by transmission electron microscopy. They are identified as (Ti, Zr) 6 Si 3 distributed mainly at the α/β interface with the size of 100 300 nm. The fine αprecipitates are detected in BMZ by electron diffraction; there was no α detected in RZ.  相似文献   

5.
In this study, we investigated the surface characteristics of the TiN/ZrN-coated nanotubular structure on Ti-35Ta-xHf ternary alloys for bio-implant applications. These ternary alloys contained from 3 wt.% to 15 wt.% Hf contents and were manufactured in an arc-melting furnace. The Ti-35Ta-xHf alloys were heat treated in Ar atmosphere at 1000 °C for 24 h, followed by water quenching. Formation of the nanotubular structure was achieved by an electrochemical method in 1 M H3PO4 electrolytes containing 0.8 wt.% NaF. The TiN coating and ZrN coating were subsequently prepared by DC-sputtering on the nanotubular surface. Microstructures and nanotubular morphology of the alloys were examined by FE-SEM, EDX and XRD. The microstructure showed a duplex (α′′ + β) phase structure. Traces of martensite disappeared with increasing Hf content, and the Ti-35Nb-15Hf alloy had an entirely equiaxed structure of β phase. This research has shown that highly ordered, high aspect ratio, and nanotubular morphology surface oxide layers can be formed on the ternary titanium alloys by anodization. The TiN and ZrN coatings formed on the nanotubular surfaces were uniform and stable. The top of the nanotube layers was uniformly covered with the ZrN film compared to the TiN film when the Ti-35Ta-xHf alloys had high Hf content.  相似文献   

6.
郑晓航  隋解和  杨哲一  张治国  蔡伟 《中国物理 B》2017,26(5):56103-056103
The effect of thermo-mechanical treatment on microstructure evolution, martensite transformation, and shape memory behavior of Ti–15Ta–15Zr high temperature shape memory alloy were investigated. Different martensite morphologies were found with different annealing temperatures. The Ti–15Ta–15Zr alloy exhibits almost perfect shape memory recovery strain of 6% after annealing at 973 K for 0.5 h.  相似文献   

7.
Electrochemical characteristics of a titanium nitride (TiN)-coated/nanotube-formed Ti-Ta-Zr alloy for biomaterials have been researched by using the magnetic sputter and electrochemical methods. Ti-30Ta-xZr (x = 3, 7 and 15 wt%) alloys were prepared by arc melting and heat treated for 24 h at 1000 °C in an argon atmosphere and then water quenching. The formation of oxide nanotubes was achieved by anodizing a Ti-30Ta-xZr alloy in H3PO4 electrolytes containing small amounts of fluoride ions at room temperature. Anodization was carried out using a scanning potentiostat, and all experiments were conducted at room temperature. The microstructure and morphology of nanotube arrays were characterized by optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The TiN coatings were obtained by the radio-frequency (RF) magnetron sputtering technique. The depositions were performed from pure Ti targets on Ti-30Ta-xZr alloys substrates. The corrosion properties of the specimens were examined using potentiodynamic test in a 0.9% NaCl solution by using potentiostat. The microstructures of Ti-30Ta-xZr alloys were changed from an equiaxed to a needle-like structure with increasing Zr content. The interspace between the nanotubes was approximately 20, 80 and 200 nm for Zr contents of 3, 7 and 15 wt%, respectively. The corrosion resistance of the TiN-coated on the anodized Ti-30Ta-xZr alloys was higher than that of the untreated Ti alloys, indicating a better protective effect.  相似文献   

8.
Microstructure and texture are known to undergo drastic modifications due to trace hypoeutectic boron addition (~0.1 wt.%) for various titanium alloys e.g. Ti–6Al–4V. The deformation behaviour of such an alloy Ti–6Al–4V–0.1B is investigated in the (α?+?β) phase field and compared against that of the base alloy Ti–6Al–4V studied under selfsame conditions. The deformation microstructures for the two alloys display bending and kinking of α lamellae in near α and softening via globularization of α lamella in near β phase regimes, respectively. The transition temperature at which pure slip based deformation changes to softening is lower for the boron added alloy. The presence of TiB particles is largely held attributable for the early softening of Ti–6Al–4V–0.1B alloy. The compression texture of both the alloys carry signature of pure α phase defamation at lower temperature and α→β→α phase transformation near the β transus temperature. Texture is influenced by a complex interplay of the deformation and transformation processes in the intermediate temperature range. The contribution from phase transformation is prominent for Ti–6Al–4V–0.1B alloy at comparatively lower temperature.  相似文献   

9.
采用单辊旋淬法制备了快速凝固Cu-1.5%Be合金(Be质量分数1.5%)薄带。根据热传输平衡方程对快速凝固冷却速率进行了估算,并借助X射线衍射仪、扫描电子显微镜对该合金的微观结构及相选择进行了分析。结果表明:当辊面线速度在29.93~39.19 m/s范围内时,合金冷却速率可达到9.80105~1.63106 K/s;随着辊轮转速的提高和喷注气压的减小,合金条带厚度和晶粒度逐渐变小;随着冷却速率的增加,溶质截留效果显著,合金相结构由复相向单相转变,当辊面线速度达到34.54 m/s时,Cu-1.5%Be合金可形成过饱和的-Cu固溶体组织,且组织细小均匀,可获得纳米晶;条带横断面显微组织由接近辊面一侧的细小等轴晶区、中间的柱状晶区和靠近自由表面的等轴晶区组成。  相似文献   

10.
The microstructure and residual stress of laser rapid formed (LRFed) nickel-base superalloy Inconel 718 was investigated. The as-deposited microstructure of an LRFed Inconel 718 alloy is composed of columnar dendrites growing epitaxially along the deposition direction, and the columnar dendrites transformed to unevenly distributed equiaxed grains after annealing treatment at high temperature. Residual stress evaluation in microstructure scale by Vickers micro-indentation method indicates that the residual thermal stress is unevenly distributed in the LRFed sample, and it has a significant effect on the recrystallization during solution annealing treatment. The residual stress is introduced by rapid heating and cooling during laser rapid forming. There is an alternative distribution between high residual stress regions and low residual stress regions, within a single deposited layer, resulting in a similar distribution of recrystallized grain size.  相似文献   

11.
急冷快速凝固过程中液相流动与组织形成的相关规律   总被引:12,自引:0,他引:12       下载免费PDF全文
徐锦锋  魏炳波 《物理学报》2004,53(6):1909-1915
研究了Fe58wt%Sn过偏晶合金的急冷快速凝固和组织形成特征. 实验发现, FeSn过偏晶合金的急冷快速凝固组织由规则排布的纤维状β-Sn相和分布其间的α-Fe相及少量金属间化合物相组成, β-Sn相的几何排列方向与合金条带表面成0—15°的夹角.根据急冷条件下金属熔体的热传导方程和Navier-Stokes方程, 对过偏晶合金的凝固行为和组织形成过程进行了理论分析, 揭示出熔体内部的动量传输对过偏晶合金的液相分离行为具有显著的影响.两相分离发生于液池底部约200μm的急冷区内, 分离的L2液滴在辊面驱 关键词: 液态 相分离 液相流动 快速凝固 晶体生长  相似文献   

12.
采用耦合群体动力学方法与元胞自动机方法建立了细化处理条件下铝合金凝固微观组织演变的数值模型.该模型考虑了a-Al的非均匀形核过程、晶粒的初始球形长大以及之后的枝晶生长过程.利用建立的模型模拟了Al-5Ti-1B中间合金细化工业纯铝凝固组织演变过程.结果表明:形核初始阶段,熔体中存在充足数量的有效形核粒子, a-Al形核率随着熔体过冷度的增大逐渐增高;形核开始不久后, a-Al的异质形核过程由熔体中有效形核粒子数量控制,直到再辉发生,形核停止.模拟分析了中间合金添加量以及熔体冷却速度对工业纯铝凝固组织演变过程的影响,模拟结果与实验结果相符,验证了模型的准确性.  相似文献   

13.
The effects of water quenching process on the microstructure and magnetic property of cold rolled dual phase steel are investigated. Correlations of microstructure, magnetic properties and water quenching parameters are established. The results show that the microstructure of the dual phase steels mainly consists of the ferrite and martensite phase, the martensite volume fraction increases gradually on increasing the holding and quenching temperature. It is found that magnetic properties of dual phase steel are very sensitive to the quenching process. Based on the minor hysteresis loop results, the coercivity and hysteresis loss increase obviously with the increase of quenching temperature, while the remanent induction and the maximum permeability tend to decrease. Furthermore, the magnetic domain structure of the ferrite phase in the presented dual phase steel is observed by magnetic force microscopy. The mechanism of the magnetic property varying with the quenching process is also discussed.  相似文献   

14.
Effects of hydrogen on microstructure characteristics and precipitation behavior have been investigated in Ti600 alloy hydrogenated at 750°C. Due to the precipitation of δ hydride and α martensite, X-ray diffraction (XRD) peaks of α phase shifted to lower angles and became broadened. XRD data showed that the addition of hydrogen expanded crystal lattice of α phase and lattice volume increased linearly in the range of 0?C H?″ martensite and δ hydride. Compared to as-received one, microstructure of hydrogenated Ti600 alloy changed obviously. Equiaxed α phase decreased and even vanished with hydrogen contents increasing. Parallel fine lamellar structure appeared and the colonies were constructed by different orientation. Micro-hardness of hydrogenated Ti600 alloy increased with the increase of hydrogen concentration, and it was considered that interstitial solution strengthening, precipitation of δ hydride, and generation of defects were the major factors.  相似文献   

15.
The viscose flow and microstructure formation of Fe-Cu peritectic alloy melts are investigated by analyzing the velocity and temperature fields during rapid solidification, which is verified by rapid quenching experiments. It is found that a large temperature gradient exists along the vertical direction of melt puddle, whereas there is no obvious temperature variation in the tangent direction of roller surface. After being sprayed from a nozzle, the alloy melt changes the magnitude and direction of its flow and velocity rapidly at a height of about 180 μm. The horizontal flow velocity increases rapidly, but the vertical flow velocity decreases sharply. A thermal boundary layer with 160–300 μm in height and a momentum boundary layer with 160–240 μm in thickness are formed at the bottom of melt puddle, and the Reynolds number Re is in the range of 870 to 1070 in the boundary layer. With the increase of Re number, the cooling rate increases linearly and the thickness of thermal boundary layer increases monotonically. The thickness of momentum boundary layer decreases slowly at first, then rises slightly and decreases sharply. If Re < 1024, the liquid flow has remarkable effects on the microstructure formation due to dominant momentum transfer. The separated liquid phase is likely to form a fiber-like microstructure. If Re>1024, the heat transfer becomes dominating and the liquid phase flow is suppressed, which results in the formation of fine and uniform equiaxed microstructures. Supported by the National Natural Science Foundation of China (Grant Nos. 50121101 and 50395105)  相似文献   

16.
Mn—Cu系阻尼合金兼有较高的阻尼特性和良好的力学性质,因而具有较大的实用前景。这类合金通常经过铸造,塑性加工和热处理来获得要求的性能和组织。加工后的Mn—Cu合金存在一个特定温度,在此温度以上合金的阻尼性能将会消失,因而影响了合金的在较高温度下的使用。该温度和合金的Mn含量有关,然而提高合金的Mn含量有会降低合金的加工性及力学性能。一般Mn-Cu合金的热处理都是利用400℃附近的时效来获得相分解后的局部高Mn组织。但是目前的时效处理后的Mn—Cu阻尼合金的最高使用温度只在80℃以下。为解决Mn—Cu阻尼合金使用温度的局限性,本研究选用凝固过程控制的方法在铸造组织中来获得较大幅度的Mn含量分布。从而在Mn-Cu合金得到较高的高阻尼特性温度。本工作利用铸型温度控制的方法,将M2052(Mn-20Cu-5Ni-2Fe)合金在250~0.1K/s冷却速度范围内控制凝固。随凝固冷却速度的降低在合金的铸态组织中观察到二次枝晶间距和晶粒尺寸的明显增大。同时还发现缓冷凝固的合金的成分比快冷凝固有较大的分布幅度。铸态下的合金阻尼性能评价也证实了凝固冷却速度对合金的凝固组织有很大的影响。尽管铸态组织的合金的高温阻尼性能并没有很大的改善,然而通过对铸态组织实施时效处理后发现缓冷凝固合金的高温阻尼性能有很大的改善。凝固冷却速度对时效处理后合金的阻尼性能有明显的影响。实验结果表明0.1K/s的冷却速度下缓慢凝固的合金在时效处理后高阻尼特性可持续高达120℃.  相似文献   

17.
The solid-state β→β?+?α transformation in titanium alloys leads to complex microstructures with feature spanning across a range of length scales. In order to develop a better understanding of the microstructural evolution process, a detailed characterization of the crystallography of α laths formed from the β phase in a candidate α/β Ti alloy, Timetal 550, has been carried out. Specifically, the influence of the orientation relationship (OR) between the grain boundary α (GB α) and the adjacent β grains on the microstructural evolution has been investigated in this alloy employing orientation imaging microscopy (OIM) studies in a high-resolution SEM. The results indicate that the colony microstructure (clustering of α laths belonging to the same variant) tends to develop in the β grain that exhibits the Burgers OR with the GB α allotriomorph, whereas the basketweave microstructure (clustering of multiple variants) develops in the adjacent β grain. Additionally, the multiple variants of α laths forming the basketweave microstructure appear to be related by certain selection criteria.  相似文献   

18.
Ti-6Al-4V合金中片层组织形成的相场模拟   总被引:3,自引:0,他引:3       下载免费PDF全文
王刚  徐东生  杨锐 《物理学报》2009,58(13):343-S348
Ti-6Al-4V是典型的α+β钛合金,不同热处理制度和热加工工艺下可得到形貌各异的微观组织,从而表现出不同的力学性能,深刻理解合金中微观组织的形成机制有助于合金的进一步优化和改造.采用相场方法模拟Ti-6Al-4V合金中片层组织的形成及演化,以热力学数据库和动力学数据库为输入,通过计算定量预测β晶界上已存在初生α相时合金组织随时间的演化.结果表明,在一定条件下,随着时间的延长晶界α向β晶内生长形成片层组织,片状α簇的形貌与界面能各向异性密切相关;晶界取向对片层生长有重要作用,垂直于晶界生长时产生最密集的片层,随倾斜角增大片层加厚且生长缓慢;此外,热处理温度显著改变片层组织形貌,温度越高,片层尖端生长速度越慢,片层间距越大. 关键词: Ti-6Al-4V 相场模拟 片层组织  相似文献   

19.
A new methodology has been established for identification of β-transus temperature in α + β and β titanium alloys by ultrasonic velocity measurements in a single specimen in one microstructural condition only. This methodology is based on a linear correlation obtained for the variation in β-transus temperature with ultrasonic longitudinal wave velocity in various titanium alloys specimens, β-heat-treated followed by water quenching. Furthermore, it has been demonstrated for the first time that ultrasonic velocity in α′ martensitic structure increases with the addition of α-stabilizing elements and decreases with the addition of β-stabilizing elements for α + β titanium-alloys.  相似文献   

20.
This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating calcium ions (Ca) obtained by hydrothermal treatment with or without post heat-treatment in the Ti-13Nb-13Zr alloy. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. In vitro biocompatibility of the Ca-containing surfaces was assessed in comparison with untreated surfaces using a pre-osteoblast cell line. Hydrothermal treatment produced a crystalline CaTiO3 layer. Post heat-treatment at 400 °C for 2 h in air significantly decreased water contact angles in the CaTiO3 layer (p < 0.001). The Ca-incorporated alloy surfaces displayed markedly increased cell viability and ALP activity compared with untreated surfaces (p < 0.001), and also an upregulated expression of various integrin genes (α1, α2, α5, αv, β1 and β3) at an early incubation time-point. Post heat-treatment further increased attachment and ALP activity in cells grown on Ca-incorporated Ti-13Nb-13Zr alloy surfaces. The results indicate that the Ca-incorporated oxide layer produced by hydrothermal treatment and a simple post heat-treatment may be effective in improving bone healing in Ti-13Nb-13Zr alloy implants by enhancing the viability and differentiation of osteoblastic cells.  相似文献   

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